Anyone tryed modding a guitar tube amp for bass

[spaners]

Hey anyone tried this. I have an epi Vj and a Fender Excelsior that I have been modding with very good results so was just wondering what others had tried ?

[Mr. Foxen]

Shouldn't really need modding, if they are close enough to be worth modding. Basically, the output transformer and power supply are the limiting factors and replacing those is going to cost more than an amp.

[spaners]

Ahh common misconception. I just bought an output transformer direct from Hammond, to go in my Fender excelsior combo (13w) Its the 1650F upto 25W [size=4]Frequency response 30 Hz. to 30 Khz. at full rated power , just over £60 quid direct from Hammond. Not a fortune in my book. As for the power transform, that seems to have more than enough umph for the job. I have made a few mods to the power supply circuit, larger capacitor just to stiffen up the low frequency's. I removed the two sag resistors (there to mimic the sag in voltage supply with a tube rectifier) Bass notes do need more power so sag not required. and a change of resistor on the board to pull the B+ voltage back down. On the pre-amp I have replaced coupling capacitors with better quality components. I have also been playing with tone stacks as stock there is just a switch. I haven't finished this mod yet but im thinking single tone control ala traynor bassmate yba-2 and a negative feed back loop (switched). I mainly plug into my RS112 (sounds good and loud ) Looking out for a speaker upgrade though for the combo although the original speaker aint to bad at low volumes it dose start to fart out quiet quickly. My plan is to use this amp with a Fender Bass IV (looking for a red one soon as funds available) hence the amp needs to be kind of a cross-over between bass and guitar. Oh I have re-covered the amp too, didn't like the original brown vinle . its red now but the re-cover made little difference to the tone lol. I have also replaced the pre-amp and out-put Tubes with Grove tubes (but who would leave the OEM tubes is any budget amp, and that includes the likes of the tiny terror too) cost wise im still under the price of an Ashdown LB30 or CTM15 . Oh n did I say it sounds great ![/size]

[paul_5]

No, simply because of the dangerous voltages inside of them.

Reading through your post though, it looks like you know what you're doing, so more power to your elbow, glad you're enjoying the sounds!

[Mr. Foxen]

[quote name='spaners' timestamp='1374943258' post='2155096']
Ahh common misconception. I just bought an output transformer direct from Hammond, to go in my Fender excelsior combo (13w) Its the 1650F upto 25W [size=4]Frequency response 30 Hz. to 30 Khz. at full rated power , just over £60 quid direct from Hammond. Not a fortune in my book. As for the power transform, that seems to have more than enough umph for the job. I have made a few mods to the power supply circuit, larger capacitor just to stiffen up the low frequency's. I removed the two sag resistors (there to mimic the sag in voltage supply with a tube rectifier) Bass notes do need more power so sag not required. and a change of resistor on the board to pull the B+ voltage back down. On the pre-amp I have replaced coupling capacitors with better quality components. I have also been playing with tone stacks as stock there is just a switch. I haven't finished this mod yet but im thinking single tone control ala traynor bassmate yba-2 and a negative feed back loop (switched). I mainly plug into my RS112 (sounds good and loud ) Looking out for a speaker upgrade though for the combo although the original speaker aint to bad at low volumes it dose start to fart out quiet quickly. My plan is to use this amp with a Fender Bass IV (looking for a red one soon as funds available) hence the amp needs to be kind of a cross-over between bass and guitar. Oh I have re-covered the amp too, didn't like the original brown vinle . its red now but the re-cover made little difference to the tone lol. I have also replaced the pre-amp and out-put Tubes with Grove tubes (but who would leave the OEM tubes is any budget amp, and that includes the likes of the tiny terror too) cost wise im still under the price of an Ashdown LB30 or CTM15 . Oh n did I say it sounds great ![/size]
[/quote]

Fender Excelsior + £60 transformer already totals more than getting a valve bass head. Before considering the other parts and labour.

[spaners]

I am fortunate to have a reasonable understanding of the components and dangers of the high voltages that can be stored inside the components of a valve amp, But I do agree that the untrained should not be messing about inside an amp without proper supervision. That said most modern amps are designed to bleed away these dangerous voltages within a short time. Even so one should always test these levels before starting any work and only experienced techs should be working inside an amp of ANY type when connected to live power.

[spaners]

Mr Foxen . I take it you have found some relatively inexpencive all tube bass amps. I have looked several times but could only ever find the LB 30s. are there others I have missed ?

[Mr. Foxen]

See links in sig. But the LB30 is one, after £350 for mine with a cover.

[6v6]

[quote name='spaners' timestamp='1375044535' post='2156172']
Mr Foxen . I take it you have found some relatively inexpencive all tube bass amps. I have looked several times but could only ever find the LB 30s. are there others I have missed ?
[/quote]

There are lots, my personal favourite is the later Traynor YBA1's - they have a lift of lid so you can easily mod them without taking the chassis out.

You could also consider building one from scratch, which is a good way to learn and keep costs down (particularly if you go for a basic hammond chassis and no fancy engraved plates etc)

[Mr. Foxen]

Had a count up recently, over 60 amps, mostly bought sub £300 aside from massive ones and big name jobs.

[spaners]

[quote name='Mr. Foxen' timestamp='1375101355' post='2156657']
Had a count up recently, over 60 amps, mostly bought sub £300 aside from massive ones and big name jobs.
[/quote]
That is an awesome collection. would like to get my hands on a Traynor, I have been thinking about modding the excelsiour bassed on one of the smaller Traynors or building a clone from scratch