Tubelab SPP first timer build

[calpe]

If you can get the SOVTEK EL84M, go for it, it seems to be a modern build of the 6P14P-EV, which is famous for durability and quality.

Hi, i'm not actually after more watts, and as we know the Tubelab SSP is a suitable 25W amp.
Is the EL84M a direct equivalent? It does say on this link, that the EL84M's - 'Sovtek EL84M lifetime is estimated to be 5000 hours versus 3000 hours for a standard Sovtek EL84.'
https://valvetubeguitaramps.com/sovtek-el84m/#:~:text=Sovtek EL84 and EL84M Summary Specification Sheet The,to gig in the back of a van.

I don't plan to alter any bias on any of the valves. I just want a 'straight forward build' switch on and enjoy 'valve' sound.
I would imagine that the Tubelab design runs the valves within their comfort zone and are not pushed hard.

 

[Steve Morley]

I don't mind the modern EL84s. Sure the 6P14-EVs are a bit "better" but to me not worth the time to search them out and the premium prices. One of the best EL84 amps I've heard (it had some fancy Mundorf $ilver-Oil caps) used bog-standard Electro-Harmonix tubes. One of my SPP builds sounded darn close though.

calpe:
The Harma EL84 tubes on your list look like selected russian tubes. Ditto the Groove Tubes 5AR4.

The Harma and Siemens ECC81s would appear to be NOS East German RFT tubes. If so I've used RFTs and found them decent and sort of channel the old Telefunken smoothness sort of vibe.

S.

 

[jcalvarez]

Hi, i'm not actually after more watts, and as we know the Tubelab SSP is a suitable 25W amp.
Is the EL84M a direct equivalent? It does say on this link, that the EL84M's - 'Sovtek EL84M lifetime is estimated to be 5000 hours versus 3000 hours for a standard Sovtek EL84.'
https://valvetubeguitaramps.com/sovtek-el84m/#:~:text=Sovtek EL84 and EL84M Summary Specification Sheet The,to gig in the back of a van.

I don't plan to alter any bias on any of the valves. I just want a 'straight forward build' switch on and enjoy 'valve' sound.
I would imagine that the Tubelab design runs the valves within their comfort zone and are not pushed hard.

Electrically they are the same, no need for schematic changes or anything. Just a slightly better tube, as Steve Morley said.
It does have a price premium though, so if you are not interested in cranking things up a bit, then the normal EL84 version is perfectly fine (and cheaper).

 

[calpe]

I'll be confirming my order with https://primarywindings.com/ and they give a 3 year warranty, and will make me the 1.5H 200mA choke too.

Perhaps i'm doing things backwards....

I'm now close to ordering the Valves (bottles/tubes) and will probably stick with the normal EL84's.
Will begin to look at a straight forward 2U/3U case. Though perhaps a 2U case will not give me enough inside height to hang the Tubelab PCB and insert the components comfortably and also for the valves to protrude through the top cover.

Once done i'll look at the smaller pieces, resistors, capacitors etc.

 

[Steve Morley]

Calpe,

If you are going to order from Watford valves, you might want to get the valve sockets there too:

https://watfordvalves.com/product_detail.asp?id=2374

Belton make some of the best, reasonably-priced sockets. Better than the generic ceramic 9-pins.

Unfortunately, the Belton octal has a strange pin diameter but this one for the rectifier will work fine:
https://watfordvalves.com/product_detail.asp?id=4756

 

[calpe]

Trying to sort out remaining parts from one supplier!

Can some one advise on why different types of resistors Case/Package are used?
e.g. Metal Oxide - Metal Film

I assuming it's a noise factor. But if this was the case then why not stick to the least noisiest resistor Case/Package Metal Film?
Sadly some values appearing in Mouser in packs of 100!
Do i assume different Manufacturers will be ok?

 

[Steve Morley]

Calpe,

Mouser used to sell Xicons in small quantities but no longer.

Generally speaking, component noise is not that much of an issue on a power amp. Also, carbon film or metal film are preferred to metal oxide in the signal path, according to generally accepted wisdom. Metal oxide can be used if you can't get the power rating in a carbon film or metal film. For the most part 5% tolerance is OK (carbon film) but metal film if you need 1% EG. feedback resistor, R104.

Here's a list of recently ordered Mouser resistors for an old amp I'm changing over to a SPP circuit. It's not complete but will you somewhere to start:

660-MOS1CT528R303J R3 30K 1W

279-CFR200J150K R4 150K 2W

660-CFS1/2CT26A224J R100, R200 220K 1/2W

660-CF1/2C102J R101, R201, R111, R211, R115, R215 1K 1/2W

660-CF1/2C221J R102, R202, 220Ω 1/2W

660-CF1/2C101J R103, R203, R105, R205 100Ω 1/2W

594-5093NW75K00J R106, R206 75K 3W

594-5083NW24K00J R107, R207, R108, R208 24K 2W

660-SPR1CT52R152J R109, R209 1.5K 1W

660-CF1/2C474J R110, R210, R114, R214 470K 1/2W

594-AC05W300R0J R112, R212, R116, R216 300Ω 5W****

594-AC05W270R0J as above 270Ω 5W****

660-SPR2CT521R101J 4 R113, R213, R117, R217 100 2W

**** I ordered 300 ohm EL84 cathode resistors as well as 270s in case the dissipation gets too high and required a change

 

[vinylkid58]

Sadly some values appearing in Mouser in packs of 100!

You can always order resistors individually. You must be on the wrong page or something.

Could have sworn there was a BOM for the SPP?

jeff

 

[Steve Morley]

Mouser changed the minimum quantities on Xicon resistors some time back. Minimum of 100 from what I could tell. For example, search: 294-100K-RC

 

[calpe]

Another boring fact, but i suspected it would happen!
I left the smaller, cheaper items to last. Why?
I can't find one single supplier that can supply all of the components for the Tubelab SSP!
Unbelievable, but i knew it would happen.

Tubelab have a 'parts list' http://tubelab.com/designs/tubelab-spp/parts-list/

Even C1 = 47uF 450V, in the Tubelab parts list (P7422-ND) from Digikey is listed as 'This product is no longer manufactured'

More troubles ahead!

 

[tonyp063]

This one would work fine

https://www.digikey.com/en/products/detail/cornell-dubilier-electronics-cde/380LX470M450H202/4927795

as would this.

https://www.digikey.com/en/products/detail/würth-elektronik/861021483002/5147673

 

[vinylkid58]

Here's a 3000 hrs/105 C : https://www.digikey.ca/en/products/detail/cornell-dubilier-electronics-cde/381LX470M450H022/1700562

jeff

 

[Steve Morley]

calpe,

A word of advice, don't order any capacitors (and therefore resistors) until you get your SPP board. Use the search functions on Digikey or Mouser, or wherever you are ordering from, and specify capacitance, voltage, style (radial) and lead spacing. Once you get a selection from your search make sure the diameter especially will fit in the space allotted on the board. You don't want to wind up with a squat little cap that will crowd other components.

Parts manufacturers discontinue and introduce new on a regular basis. Unfortunately, Digikey, Mouser, etc. don't recommend a replacement for a discontinued part. For that reason parts list have, what is essentially, a best before date.

Not to sound like a jerk but, it's called DIY for a reason. Once you develop your list (once upon a time I was able to buy all SPP caps and resistors from Mouser) share it with the community to help the next SPP builder.

Best, Steve

 

[vinylkid58]

Once you get a selection from your search make sure the diameter especially will fit in the space allotted on the board. You don't want to wind up with a squat little cap that will crowd other components.

I got 35 hits for the 47uf 450v cap on Digikey. They were all the same diameter (22mm), just differing heights.

jeff

 

[calpe]

I need the SPP PCB to arrive!
George of Tubelabs sent it on the 13th July 2022, but still has not arrived.

UPS states 'July 28, 2022, 7:10 pm, Processed Through Facility. UNITED KINGDOM
Your item was processed through a facility in UNITED KINGDOM on July 28, 2022 at 7:10 pm. The item is currently in transit to the destination.'

In limited time i do hope to sort out the resistors/capacitors etc etc. over the weekend......

 

[calpe]

Confirmed! SPP PCB has arrived, need to get Post Office notification to be able to collect it.
Severely delayed in the U.K.
Happy Days....

 

[calpe]

calpe,
A word of advice, don't order any capacitors (and therefore resistors) until you get your SPP board. Use the search functions on Digikey or Mouser, or wherever you are ordering from, and specify capacitance, voltage, style (radial) and lead spacing. Once you get a selection from your search make sure the diameter especially will fit in the space allotted on the board. You don't want to wind up with a squat little cap that will crowd other components.

Not to sound like a jerk but, it's called DIY for a reason. Once you develop your list (once upon a time I was able to buy all SPP caps and resistors from Mouser) share it with the community to help the next SPP builder.

I have spent some time this afternoon checking through Tubelabs part list, finally.

Your right, DIY it is...... i haven't build anything for 4/5 years now, wish i had the expertise of Stephe, it looks so easy!
I insisted to the missus that this is one important project (and probably my last) and i need time to get things right.
Appreciate your advise Steve. I am actually checking dimensions etc before i've added parts on 'My List' in DigiKey.

Digikey don't have these: -
R104/204 - 5.1K 1/4W metal film
R102/202 - 220R 1/4W metal film
R106/206 - 75K 3W metal oxide

C1 - 47uF 450V i will order 338-3659-ND
C2 - 150uF 450V i will order 339-1939-ND

Some of the remaining capacitors i'll need to order similar types as quoted in the Tubelab parts list.
As it's been mentioned by Steve, if original type is not available check dimensions and spec, to be able to order a replacement.

The case i'll probably get a 3U case, nothing expensive, but something that does the job.
I won't pick anything fancy / flashy, but practical yes!
The SPP PCB i wish to place under the top plate of the case, to have on view those glowing (not to bright) red glass things called Valves.

Bits and bobs still to sort out - screws, nuts, grommets.......

Thanks to you all.

 

[calpe]

The diodes in series with the GZ34 became required on the SSE and were added to the board in 2010. The SSE runs the rectifier hard and the three major suppliers of new production tubes were turning out junk at the time. SPP builders have not reported repeated rectifier tube failures like the SSE builders did, so the diodes were never added to the SPP board. The builder could solder a 1N4007 to the end of each red transformer wire and cover it with heat shrink to accomplish the same thing.

George, just to ask if the diodes (HER108's - Rectifiers 1A 1000V, low noise) suggested by John Broskie would be a good idea to fit?
I believe it slows the immediate output of the B+ on switch on.

 

[Steve Morley]

R104/204 - 5.1K 1/4W metal film:
RNMF14FTC5K10 or RNMF14FAD5K10 or MBA02040C5101FCT00

R102/202 - 220R 1/4W metal film:
MFR-25FBF52-220R
MFR-25FTE52-220R
RNMF14FTC220R

If 1/4 watt not available go to 1/2 watt.

R106/206 - 75K 3W metal oxide
Try metal film: RR03J75KTB

Diodes won't slow B+, The 5AR4 does that.

In my builds the board is suspended from the case top. I forget the spacers I used, 1/2", 3/4"? Lots of tube sticking through the top. Once you decide on the spacers the 150UF cap, mounted on the bottom side of the board, will determine the interior chassis height you will need.

Cheers, S.

 

[calpe]

George (Tubelab) told us about C101 .....
"The capacitor is used to tweak the feedback compensation for the high frequencies. The usual way to do this is to apply a 10 KHz square wave to the amp with a resistive dummy load attached and tweak the cap value for the best square wave with a scope.
I have seen values from 270 pF to 880 pF work the best using the scope and square wave method. The value depends on the OPT being used. It you must guess, start with 470 pF. That is probably better than no cap".

Might anyone know what type of capacitor it is?
I'll probably order a couple of values to play safe.